1. Technical Field
The present invention relates to compact ovens in general, and in particular to a compact oven having a high volume of even airflow with tight columns of air impingement.
2. Description of Related Art
For a conventional oven, the profile of the heat energy for cooking food items located inside a cavity of the oven is typically determined by the mechanical configuration of a heating source. For example, a conventional oven may contain one or more variable speed blowers that can be set at a specific rotations per minute (RPM) to deliver a given volume of heated air via one or more plenums. The temperature of the rapidly moving heated air can be readily maintained at or near a temperature set by a temperature control feedback loop.
In order to accelerate cook time, some ovens employ a technique known as air impingement. Air impingement can be achieved by moving heated air rapidly from one or more plenums through a set of nozzles located in the periphery of an oven cavity, thereby causing columns of the heated air to come into more direct contact with a food item as the heated air pierces the temperature gradients that surround the food item placed within the oven cavity. Since tighter columns of air at the food surface can improve the rate of heat transfer from the impinging air, cooking times are reduced as a result. Increasing airflow volume, which is typically measured in cubic feet per minute (CFM), can further reduce cook times of a food item because more hot air mass can be moved past the surface of the food item, thereby improving the rate of heat transfer to the food item.
There are many challenges, however, to achieving tighter columns and higher CFM of heated air inside an oven cavity. At a given blower speed, reducing nozzle size increases air velocity, thereby tightening the air columns, but the air volume is also reduced due to the increase in back pressure caused by the reduced nozzle size. The opposite is true as well—at a given blower speed, increased nozzle size increases air volume but reduces air velocity through the nozzles and loosens the air columns that are important to the air impingement process. Increased blower speed is a commonly used alternative, but this method is problematic in smaller ovens where elevated blower speeds cause uneven air distribution in a relatively small blower plenum.